Alex Fowler, Mozilla's technology and privacy officer, said in a blog post that Firefox's upcoming Do Not Track feature will be the nonprofit group's first step toward improving user privacy.

"When the feature is enabled and users turn it on, web sites will be told by Firefox that a user would like to opt-out of OBA [online behavioral advertising]," Fowler wrote. "We believe the header-based approach has the potential to be better for the web in the long run because it is a clearer and more universal opt-out mechanism than cookies or blacklists."

Sean Harvey and Rajas Moonka, two Google product managers, wrote that Keep My Opt-Outs will allow users to opt out of tracking from advertisers by way of a downloadable browser extension that will allow users to defer from personalized ads "from all participating ad networks only once and store that setting permanently."

Both Google and Mozilla's tracking blocking tools do, however, have a caveat.

The tools only apply to advertising companies that offer opt-out options. So far, advertisers have been slow to add such options themselves, though Google noted that the advertisers that are members of the Network Advertising Initiative offer such options, as do some Web advertising trade associations.

Web advertisers track which websites consumers visit online in large part to offer Web ads that would appeal to a user based on the user's surfing habits.

Google said once its Keep My Opt-Outs feature could lead to users seeing repeat ads or ads that are less relevant to their interests. Google, a major seller of Web advertising, also offers the option of users tailoring ads they see in Chrome by telling the Mountain View-based company what types of ads they'd like to see.